Overhead crane

ABSTRACT

An overhead crane characterized by its redundant or double-safe features. The crane has two separate ropes with one end of each rope attached to the drum and the other end attached to an equalizer. Each rope, intermediate its opposite ends, is reeved over sheaves in the sheave nest and on the load block in such manner that each rope provides at least four active parts (i.e., load-supporting lines) running to the four horizontal quadrants of the load block with respect to the vertical center line therethrough. With this system and arrangement the load block will be supported by two independent sets having at least four active rope parts or lines of support in each set in such a manner that if a rope breaks or fails for any reason, at least one remaining complete set of at least four active parts provided by the undamaged rope will assume full support with little or no appreciable impact load occurring and with only small and acceptable swinging or twisting movement imparted to the lead. Additional redundancy and double-safety is provided by: constructing the crane hook so it has two separate load paths into the load block; having two complete gear trains between the hoist motor and the drum assembly with each being capable of handling the rated load with a normal factor of safety; having safety lugs to catch the drum hubs in case of shaft failure; having safety retainers for all sheaves in the sheave nest and in the load block to sustain the load upon failure of any sheave or its supporting shaft; and, having the equalizer bar boxed or caged in with load supporting members and provided with bumpers at opposite ends.

United States Patent [191 Vlazny et al.

[451 Jan. 22, 1974 52 U.S.Cl. 212/11, 254/184 [51] Int. Cl. B66c 17/06 58 FieldofSearch ..254/184,l88;212/3,l1

[56] References Cited UNITED STATES PATENTS 1,765,347 6/1930 Shepard 254/188 X 2,276,767 3/1942 Dubuque 254/188 2,973,942 3/1961 Schaper..... 254/188 2,306,055 12/1942 Harry 212/11 2,960,310 11/1960 Hull 254/188 X FOREIGN PATENTS OR APPLICATIONS 1,237,755 3/1967 Germany 254/188 Primary Examiner-Richard A. Schacher Attorney, Agent, or Firm-Fred S. Lockwood et a1.

[57] ABSTRACT An overhead crane characterized by its redundant or double-safe features. The crane has two separate ropes with one end of each rope attached to the drum and the other end attached to an equalizer. Each rope, intermediate its opposite ends, is reeved over sheaves in the sheave nest and on the load block in such manner that each rope provides at least four active parts (i.e., load-supporting lines) running to the four horizontal quadrants of the load block with respect to the vertical center line therethrough. With this system and arrangement the load block will be supported by two independent sets having at least four active rope parts or lines of support in each set in such a manner that if a rope breaks or fails for any reason, at least one remaining complete set of at least four active parts provided by the undamaged rope will assume full support with little or no appreciable impact load occurring and with only small and acceptable swinging or twisting movement imparted to the lead. Additional redundancy and double-safety is provided by: constructing the crane hook so it has two separate load paths into the load block; having two complete gear trains between the hoist motor and the drum assembly with each being capable of handling the rated load with a normal factor of safety; having safety lugs to catch the drum hubs in case of shaft failure; having safety retainers for all sheaves in the sheave nest and in the load block to sustain the load upon failure of any sheave or its supporting shaft; and, having the equalizer bar boxed or caged in with load supporting members and provided with bumpers at opposite ends.

15 Claims, 14 Drawing Figures PATENIEB JAN22 I974 SHEEIIOF] PMENTEI] JANZZ I974 SHEET 3 BF 7 PAIENT 1164221974 SHEEI 5 0f 7 g IZOF PMENTEI] JAH22 I974 saw a or 7 mommom 5N N2 OVERHEAD CRANE This invention relates generally to innovations and improvements in overhead cranes, particularly overhead traveling cranes of large capacities, whereby such cranes qualify as redundant and double-safe in respect to potential damage to or failure of any part that might possible fail, including the crane ropes.

By virtue of good design, careful maintenance and proper operation, overhead cranes have over a number of years and in a variety of applications proven to be highly useful, and often essential, machines for performing various necessary industrial and construction operations. However, in spite of the overall excellent safety record which cranes have earned and continue to justify there is a possibility of inadvertent and unforeseeable failure of the type inherent in any machine no matter how well and carefully designed, constructed, maintained and operated. Primarily, there is a possibility of rope or hook failure.

Since there are certain critical situations where failure of a crane would be especially serious, this problem of potential failure, even though remote, has received prior consideration and various solutions have been suggested. One obvious suggestion has been to provide two cranes instead of one, either one of which has adequate capacity to handle the load in case the other fails. This solution, however, has not been found acceptable for several reaons. While the double expense and investment entailed is one objection, actually this objection may not be as serious as others. One of the other more serious objections is the limitation on available space. Thus, in many situations adequate space is not avilable for installation and operation of two separate cranes. Another serious objection to suggested solutions, including that of providing two separate cranes, is the inherent problem of instant transfer of the entire load shared by two cranes or support systems to one of the cranes or support systems without appreciable impact load occurring.

If one of two separate cranes handling the same load should fail, there is a possibility of serious damage to the remaining crane as the result of an impact load occurring during the load transfer. Basically, cranes are not designed to withstand or absorb appreciable impact loads created by falling or slipping of the dead-weight loads which the cranes are designed to safely handle under normal operating conditions. Furthermore, in the event one of the two cranes should fail, even if the remaining crane is capable of safely raking on the entire load by itself, in doing so there may be excessive swinging or twisting of the load incident to the load transfer and this can have very serious consequences depending upon the nature of the load, especially if the load is being handled in closequarters.

An excellent example illustrating the foregoing difficulties and problems is presented in connection with atomic energy reactors for large electrical power generating plants where there is an infrequent but recurring need to lift and lower heavy, thick-metal wall casks containing reactor rods. If one of these caks is dropped more than its free fall capability without rupturing, it will break and expose the reactor rods, making the site unapproachable for many years. Some of the serious consequences of such an accident are readily apparent. First, there are the radiation hazards that must be avoided over a period of years. Second, there are the consequences which will result from taking out of production without notice a large segment of the normally available power supply which may already be overtaxed. Third, there is the tremendous financial loss incurred and associated with a multi-million dollar installation and investment being suddenly transformed from a valuable asset to a prolonged source of danger.

In a typical atomic energy power generating plant, an overhead traveling crane may be permanently installed at a location that is 50 or more feet above ground level. Perhaps several times a year the crane will be called upon to lift a heavy metal, thick-walled cask containing spent reactor rods from a water tank in which the fuel is located, swing the lifted cask over one side of the tank and then lower it to ground level. The problem is complicated by the fact that the activated reactor rods cannot remain uncooled for more than a few hours. Hence, the practice is to lower the cask to the ground and then promptly load it onto transporting means which is provided with cooling facilities for providing the cooling action required during transport. The reverse operation is performed when inactive regenerated reactor rods are delivered to the power plant site and have to be raised by the crane from ground level and installed in the elevated bath or water tank in the power plant. In the foregoing situation it is apparent that once the crane facilities commence the operation of transferring spent reactor rods there is an irrevocable committment that the operation must go onto completion.

In view of the foregoing illustrative considerations, the object of the present invention, generally stated, is the provision of a new and improved overhead crane having redundant load supporting features that will meet the safety requirements represented by situations wherein in the event of failure of a rope or some load supporting orrestraining mechanical part, the crane will still be capable of supporting the load without objectionable impact load being imparted to the residual support system and without excessive or objectionable swinging, twisting or other movement being imparted to the load.

An important and more specific object of the invention is the improvement in overhead cranes wherein redundant or double-safe ree ving is provided which allows the crane to continue in operation in the event of failure of one rope.

Another important and more specific object of the invention is the. improvement in overhead cranes wherein redundant or double-safe crane hooks are provided which permits a crane to continue in operation in the event of failure of one portion of the hook.

Certain other objects of the invention will, in part, be obvious and will, in part, appear hereinafter.

For a more complete understanding of the nature and scope of the invention, reference may now be had to the following detailed description thereof taken in connection with the accompanying drawings, wherein:

FIG. 1 is a perspective diagrammatic view of a tworope reeving arrangement and a two-path hook for an overhead crane illustrating the present invention;

FIG. 2 is a top plan view of an overhead crane incorporating a working embodiment of the present invention;

FIG. 3 is a fragmentary view taken on line 3-3 of FIG. 2, certain parts being omitted;

FIG. 4 is an elevational view, partly broken away, taken on line 4-4 of FIG. 2;

FIG. 5 is an elevational view taken on line 5-5 of FIG. 3 on an enlarged scale;

FIG. 6 is a view partly in section and partly in elevation taken on lune 6-6 of FIG. 5;

FIG. 7 is a horizontai sectional view partly in section and partly in plan taken on line 7-7 of FIG. 3;

FIG. 8 is a detail view on enlarged scale, partly in section and partly in elevation, taken on line 88 of FIG.

FIG. 9 is a view corresponding to FIG. 3 of a second working embodiment of the invention;

FIG. 10 is a view taken on line 10-10 of FIG. 9;

FIG. 11 is a view partly in elevation and partly in section of an alternate form of equalizer bar assembly that may be used in the crane shown in FIGS. 2-8;

FIG. 12 is a fragmentary detail sectional view taken on line 12-12 of FIG. 11; and

FIG. 13 and 14 are diagrammatic views of two other alternate forms of equalizer bar assemblies.

Referring to FIG. 1, a crane drum is indicated at 5 having two separate ropes 6 (shown in broken line) and 7 wound on opposite halves thereof. One end of rope 6 will be secured to the drum 5 adjacent the right end thereof while the opposite end of rope 6 will be secured to an equalizer 8 adjacent one end thereof. Similarly, one end of the rope 7 will be secured or anchored to the drum 5 adjacent the left end thereof while the opposite end of rope 7 will be anchored or secured to the equalizer 8 adjacent the right end thereof. Intermediate its anchored ends each of the ropes 6 and 7 has a separate but corresponding reeving arrangement or pattern. Considering first rope 6, it has a first active part or load supporting part 6a which descends from the drum 5 on one side of its mid-portion and passes underneath a sheave 12 which it will be understood is carried in the load block of a crane. A second active part 612 of the rope 6 passes upwardly from under the sheave 12 and runs over the top of a sheave 13 which is also in the sheave nest in the main part of the crane. A third active part 60 of the rope 6 passes downwardly from over the sheave 13 and underneath a second load block sheave 14. The fourth active part 6d of the rope 6 passes upwardly from underneath the sheave 14 and is attached at 10 to the equalizer 8. Accordingly, it will be seen that the rope 6 has four active parts or four parts 6a, 6b, 6c, and 6d in suspension between the crane itself (as represented by the sheave l3, equalizer bar 8 and drum 5) and the crane block (as represented by the sheaves 12 and 14).

Similarly, the rope 7 has an active part 70 which passes down from the drum 5 on one side of the middle and underneath a block sheave 16, a second active part 7b which passes upwardly from under the sheave 16 to a nest sheave 17, a third active part 7c which passes downwardly from over the sheave 17 to a fourth block sheave 18, and a fourth active part 7d which passes upwardly from under the sheave 18 to where it is secured at all to the equalizer bar 8.

A crane hook is so constructed that it provides two separate co-incident load paths to the crane block. One of the paths is through an outer sleeve 20 having a sister hook formation 21 at the bottom end thereof. The other path is provided by an inner core or stem 22 carrying at its bottom end an attaching eye 23. Suitable and separate means are provided for securing the sleeve 20 and the core or stem 22 to the crane block.

.The center line through the hook 15 and through the crane block is indicated at 24.

It will be seen that all of the block sheaves 12, 14, 16 and 18 lie in parallel planes with sheaves 12 and 18 being located on one side of the center line 24 or of the vertical center plane that is parallel to all the block sheaves. The other of sheaves l4 and 16 are on the opposite side of the center line 24 of the vertical center plane that is parallel to the block sheaves. In the arrangement shown, the perpendicular axes of the block sheaves 12, 14, 16 and 18 are co-axially mounted. It will also be observed that the nest sheaves 13 and 17 are aligned in parallel planes but the perpendicular axes thereof do not coincide.

It will be apparent that the horizontal diameters of the sheaves 12, 14, 16 and 18 are all parallel and lie in the same horizontal plane. With the diameters of sheaves l4 and 18 being equal and of sheave 12 and 16 being greater and equal, it will be seen that the ends of the horizontal diameters of sheaves 12 and 14 coincide with the comers of a horizontal trapezoid which extends on opposite sides of the center line 24 and of the vertical center plane which includes center line 24 and is parallel to the planes of the sheaves I2 and 14. Similarly, the ends of the horizontal diameters of sheaves 16 and 18 also will coincide with the corners of a second horizontal trapezoid which also extends on opposite sides of the vertical center plane that is parallel to the planes of the sheaves 16 and 18. The relative lengths of the sheave diameters and the positioning of the sheaves should be such that the ends of each horizontal diameter in the pairs of sheaves 12-14 and 16-18 are substantially equi-distant from the vertical center line 24 so that the moment arm of each active rope part with respect to center line 24 is substantially equal. Accordingly, it will be seen that each of the ropes 6 and 7 has four active parts or load-supporting runs with each part or run at its lower end being attached to the load block in such manner as to support the load block equally from one of its horizontal quadrants. Accordingly, in the arrangement shown in FIG. 1, each of the sets of four active parts of rope (i.e. 6a, 6b, 6c, and 6d and 7a, 7b, 7c and 7d) supports the load placed on the crane hook 1S equally with the weight being equally distributed between the two sets of active parts and being equally distributed within each set between each active rope part therein. The center of the load path provided by each set of four active rope parts is substantially coincident with the center line 24 so that the load paths of the two sets of rope parts and the load paths of the hook 15 are substantially co-incident.

In the event of breakage or failure of either rope 6 or 7 the share of the total load supported by the active runs of that rope will be immediately transferred without development of slack to the active runs of the remaining rope and without substantial impact being imparted. Furthermore, since each active rope part in each set of four attaches to the crane block in one of the four horizontal quadrants thereof at approximately the same distance from the vertical center line 24 and the load paths of the load hook and the load path of the survive set of active rope parts are substantially coincident, there will be very little swinging or twisting motion imparted to the load when the load transfer occurs. When one of the ropes 6 or 7 breaks, two types of movement .of the load on the hook 15 will occur.

There will be some vertical settling due to tilting of the equalizer bar. Suitable shock absorbers should be provided for the equalizer bar so that this movement occurs slowly without impact. The load will also swing somewhat under the drum 5 since it is now supported by only one half of the drum. This swinging movement is minimized since the remaining active rope part 6a or 7a is only one of the remaining four active rope parts.

Referring now to the embodiment shown in FIGS. 2-8, a crane is indicated generally at (FIGS. 2 and 4) which in many respects and features corresponds to a conventional overhead traveling crane of known type and comprises the main crane mechanism which operates on the superstructure a portion of which is indicated at 26 and a load block indicated generally at 27 which carries the crane hook indicated generally at 28. The crane 25 includes a reversible motor 30 for operating the crane drum 31 and a second reversible motor 32 for driving the crane trolley which includes a pair of driven wheels 33-33 which ride on parallel rails provided by the superstructure 26. A second set of nondriven wheels 34-34 provides full support of the crane mechanism on the superstructure. The drive mechanisms for the drum 31 and for the trolley wheels 33-33 are conventional but the drum drive is duplicated in order to provide redundancy.

With respect to the drum 31, drive shafts 35 and 36 extend from opposite sides of the motor 30 and, through reduction gearing of known type indicated at 3939, drive pinions 37 and 38, respectively. The drive shaft 35 drives a long shaft 40 which, depending on the control system, may be connected with an eddy current brake 41 if required for speed control. Outboard of the brake 41 on one side and of the motor 30 on the opposite side, conventional shoe brakes 42 and 43 are provided for stopping the crane drum 3] and holding it in any desired position with respect to the block 27. The pinions 37 and 38 in known manner engage and drive spur gears 45 and 46, respectively, mounted on opposite ends of the drum 31.

The sheave nest of the crane 25 has a horizontal, centrally disposed support shaft 47 supported at its opposite ends in vertical support plates 48 and 50. An equalizer beam 51 is journaled intermediate its ends on the shaft 47 by means of a sleeve bearing 52 projecting from one side of the beam 51. The sleeve 52 is carried at the apex of an inverted V-formation 53 (FIG. 3) integrally formed as part of the beam. Shock absorber units 49-49 are suitably connected with opposite ends of the beam 51 so as to dampen the tilting movement that will occur when one of the two ropes supporting the load breaks. The equalizer 51 is provided with horizontal slots 54 and 55 extending inwardly from opposite ends and also with vertical slots extending inwardly from opposite ends. The vertical slots receive the lower ends of bolts 56 and 57 which project upwardly through flanged bushings 58-58 supported by aperturned brackets 59 and 60 carried by vertical plates 61 and 62 extending in planes transverse to the plane of the equalizer 51 and disposed outwardly of the opposite ends thereof. Compression springs 63 and 64 are retained between the bushings 58-58 and washers 29-29 by nuts 39-39 screwed onto the upper ends of the bolts 56 and 57 while nuts 19-19 are screwed onto the lower ends thereof as shown so as to retain the assemblies in place. A transverse pin 65 carried by bolt 56 extends horizontally through both sides of the slot 54. Similarly, a pin 66 carried by bolt 57 extends through opposite sides of the horizontal slot 55.

' It will be seen that while with the foregoing arrangement the equalizer 51 can tilt in either direction on the shaft 47, in doing so the tilting action will be dampened by the springs 63 and 64 which act as shock absorbers. The same damping action may also be provided by known hydraulic or pneumatic shock absorbing units replacing the springs 63 and 64 as will be hereinafter described.

As shown in FIGS. 2 and 4 a pair of sheaves 70 and 71 of known type having their own bearings are mounted on the shaft 47. A pair of similar but smaller diameter sheaves 72 and 73 are also mounted on shaft 47. On the side of the vertical support plate 48 opposite from that side on which sheaves 72 and 73 are mounted, a fifth sheave 74 is mounted on a stub shaft 75 carried between the plate 48 and a parallel vertical plate 76. A sixth sheave 77 is mounted on a shaft 78 extending between plate 76 and plate 80. It will be seen that the sheaves 70, 71, 72, 73, 74 and 77 in the sheave nest lie in parallel vertical planes which are also parallel to the axis of the crane drum 31.

The load block 27 comprises a generally open frame which supports a horizontal shaft 81 on which eight block sheaves are supported in two groups of four each. The block frame comprises a pair of end plates 82 and 83 (FIGS. 5 and 6) and a pair of inboard plates 84 and 85. These plates 82, 83, 84 and 85 are supported in spaced relationship on bolts 86, 87, 88 and 90 carrying hex nuts on their outer ends. Four block sheaves 91, 92, 93 and 94 are supported on the shaft 81 in between the plates 82 and 84. Similarly, four block sheaves 95, 96, 97 and 98 are supported on the shaft 81 in between the plates 83 and 85. It will be seen that the sheaves 91, 94, 95 and 98 all have diameters larger than that of the sheaves 92, 93, 96 and 97 all of which have the same diameter. Sheaves 91 and 95 have equal diameters and the diameters of sheaves 94 and 95 are somewhat larger and equal. The upper frame bolts 86 and 87 support one set of sheave guards 100, 101 and 102 between the plates 82 and 84 and a second set of sheave guards 103, 104 and 105 between the plates 83 and 85. Each sheave guard 100, 101, 102, 103, 104, and 105 is contoured on the underside to provide running clearance over the top of its respective sheave and designed to sustain the load in the event of failure of shaft 81 or any of the sheaves mounted thereon. These sheave guards 100-105 also serve as spacers for the plates 82 and 84 and 83 and 85. Preferably, a similar sheave guard 106 (FIG. 4) is provided under sheaves 70 and 71, another sheave guard 107 under sheaves 72 and 73, another sheave guard 108 under sheave 74 and still another sheave guard 109 under sheave 77. Each of the sheave guards 106, 107, 108 and 109 is contoured at the top to provide running clearance under the bottom of its respective sheave and is also designed to sustain the load in the event of failure of shafts 47, 75 or 78 or of any of the sheaves mounted thereon.

The block 27 carries a redundant or double load path crane hook indicated generally at 28 in FIGS. 5 and 6. The hook 28 is supported on the shaft 81 of the load block 27 by means of the generally cube-shaped midportion 110 integrally formed as part of the shaft 81. Opposite sides of the cube portion 110 fit into square openings provided therefor in the plates 84 and 85. The cube portion 110 has a vertical bore extending therethrough which accommodates the outer sleeve or tube 1 1 1 of the hook 28. The upper end of the sleeve or tube 1 1 is provided with exterior threads which receive a nut 112 which screws down onto the upper part of a thrust bearing 113 of known type the bottom half of which rests on the top surface of the cube 110. At its lower end the tube 111 is provided with a sister hook formation 114. A pin or bolt 115 extends through the tube 111 and projects on opposite ends thereof. At its upper end the bolt or pin 1 is exteriorly threaded to receive a nut 1 16 which is tightened down onto the upper segment of a thrust bearing 117, the lower segment of which bears against the top of the nut 1 12. At its lower end the bolt or pin 115 is provided with an eye formation 118 of known type.

It will be seen that by means of the foregoing construction the hook 28 is redundant in having two separate load paths either of which is capable of independentiy supporting the meximum load that the crane is designed to handle. The tube 110 and the bolt 115 extending therethrough can each swivel in either direction about the same vertical axis.

The special manner in which a pair of ropes are reeved over the sheaves in the sheave nest and the sheaves in the load block 27 will how be described. As shown in FIG. 2, the drum 31 has two ropes 120 and 121 level-wound thereon with one end of each rope being secured to the drum adjacent one of the opposite outer ends thereof. The ropes 120 and 121 are wound in known manner on the drum 31 so that they unwind from the center of the drum 31 toward the opposite outer ends and conversely, wind on the drum from the opposite ends toward the center. For purposes of clarity the rope 121 is shown in full line in FIG. 3 while the rope 120 is shown in broken line therein. In FIG. 4 only rope 120 is shown.

Referring to FIGS. 3 and 4, the rope 120 is shown coming down from the mid-portion of the drum 31 in what may be referred to as rope part 120A. It passes down under block sheave 94 and then rises as rope part 1208 and passes over upper sheave 77. From sheave 77 rope 120 descends as part 120C and passes down and underneath block sheave 95. It rises as rope part 120D from under sheave 95 and passes over nest sheave 70 from which it descends as rope part 120E and passes underneath block sheave 92. From underneath block sheave 92 the rope 120 rises as rope part 120F so as to pass over nest sheave 72. The rope passes down from sheave 72 as rope part 1206 and passes underneath block sheave 97 from which it rises as rope part 120I-I. The upper end of rope part 120I-l is also end end of rope part 120 and attaches to a clevis 122 (FIG. 3) carried by another clevis 123 from underneath the equalizer 51.

From the foregoing it will be seen that the rope 120 passes between sheaves 70, 72 and 77 in the sheave nest and sheaves 92, 94, 95 and 97 in the load block 27 in eight active parts lA-l20I-I. The diameters of the various sheaves and the positions of the various sheaves over which rope 120 is reeved are such that rope parts 120B120I-l are approximately vertical at all times between the upper most position of the load block 27 and its lower most position.

Referring to FIG. 7 the ropes 120 and 121 are indicated in two different cross sections as they pass up or down at the opposite ends of the horizontal diameters of the block sheaves. It will be understood that the rope 121 is reeved around the nest sheaves 71, 73 and 74 and the block sheaves 91, 93, 96 and 98 in a pattern or manner corresponding to the reeving of rope in eight rope parts 121a-121h as indicated in FIGS. 3 and 7. The upper end of rope part 121h is attached to a clevis 124 carried on another clevis 125 pinned to the equalizer 51.

If either rope 120 or 121 should for any reason break or fail, the other rope will have eight active rope parts fully intact and supporting the load block from the crane. As will be seen from FIG. 7 the lengths of the moment arms of the eight rope parts of each rope with respect to the vertical center line of the load block 27 are such that their combined moments in the quadrants around the center line approximately equal and balance so that a load is stable and free from an objectionable degree of twisting or tilting as long as either rope 120 or 121 remains intact. If one of the ropes 120 or 121 breaks there will be some vertical settling of the load and the block 27 due to tilting of the equalizing beam 51. However, the shock absorbers 4949 function to allow the tilting to occur only gradually so that there will be little or no impact. The load and load block 27 will also swing somewhat under the drum 31 when one of the ropes 120 or 121 breaks since they will then be supported only by one half of the drum. This swinging movement is minimized since the active rope part 120A or 121a which remains to support the load under one half of the drum is only one of the remaining eight supporting rope parts. In this embodiment the slight swinging movement will be due in part to the combined moments of rope parts 120C and 120D on the right side of the load block being somewhat greater than those of rope parts 120E and 120F with the combined moments of rope parts 121a and 121d being somewhat greater than those of rope parts 121e and 121f.

Reference is now made to FIGS. 2 and 8 for the description of a further safety and redundancy feature in the event one of the shafts 126-126 supporting the drum 31 from its opposite ends should break or one of the pedestals 127-127 mounting the bearings journalling an end of a shaft 126 should become damaged in some manner. There is mounted on the frame structure directly under each drum hub 128 that supports one of the shafts 126 a safety block 129. The upper surface of each block is arcuate so as to conform to the curvature of the hub with a slight space therebetween. Since the drum- 31 will always turn in the direction of the arrow A (FIG. 8) in the event of failure, the blocks 129 need not extend entirely under its respective hub 128 in order to catch and support the hub.

Referring to FIGS. 9 and 10, a modification is shown wherein two ropes have seven support parts each with one rope part in each of two of the four quadrants around the vertical center line of the load block, with two rope parts in each of the other two of the quadrants and with the seventh rope part connected to an equalizer which is carried by the load block. In FIG. 9 the load block is indicated generally at and the crane drum is indicated generally at 136. The double-path crane hook is indicated generally at 137 and may have the same construction as the crane hook 28 in FIGS. 5

are of the same size and mounted on separate shafts 143 and 144, respectively, below and on opposite sides of the axis of sheaves 138 and 139. There are two addi- The load block 135 includes a sheave-support frame comprising vertical side members 145 and 146 with intermediate vertical plate members 147 and 148. Four corner bolts extend horizontally through the vertical plates with only one of the bolts 150 being shown. The vertical plates 145, 146, 147 and 148 support a sheave shaft 151 on which block sheaves 152, 153, 154, 155, 156 and 157 are mounted in two sets as shown. There is a spacer 158 between sheaves 152 and 153 and another spacer 160 between sheaves 155 and 156. These spacers provide the proper moment arms for the different rope parts. The crane hook 137 is supported from an integral block 161 the mid-portion of shaft 151 in the same manner that crane hook 28 is supported from the load block shaft 81 in FIGS. and 6.

The vertical plates 145, 146, 147 and 148 on their top edges support a pair of transverse plates 162 and 163 the upper edges of which incline to a peak, the peak for plate 162 being designated at 159. The plates 162 and 163 support therebetween a horizontal shaft 164 on which is mounted an equalizer 165. The opposite ends of the equalizer 165 are provided with both inwardly extending horizontal slots 166-166 and inwardly extending vertical slots (not shown), the latter being large enough to accommodate the upper ends of bolts 167-167. The bolts 167 extend downwardly through apertures in horizontal plates 168-168 carried underneath the outer ends of the vertical plates 162 and 163. The bolts 167 project a substantial distance beneath the plates 168 and carry compression springs 170-170 which are compressed between washers at opposite ends and maintained under compression by the nuts 171-171 threaded on the lower ends thereof. It will be seen that the spring assemblies serve as shock absorbers for dampening tilting movement of the equalizer 165 in either direction in the event that one of the two ropes connected thereto on opposite sides of the shaft 164 breaks. If desired, the springs 170 can be enclosed in shields 172-172.

The drum 136 has two ropes 173 and 174 wound thereon from the opposite outer ends toward the middle. For purposes of simplicity only the one part 174a of rope 174 that comes down directly from the drum 136 and the one part 174g that connects to the equalizer 165 are shown, with all seven parts 173A-G of rope 173 being shown. The first part of rope 173 that comes down from the drum 136 is indicated at 173A. This rope part passes down under the block sheave 157 and rises upwardly as rope part 173B which passes over sheave 141 in the upper sheave nest. The rope passes down from over the sheave 141 as rope part 173C around, underneath the sheave 152 and upwardly as rope part 173D. This top part passes over sheave 138 and down as rope part 173E so as to pass under sheave 156. It rises upwardly from sheave 156 as rope part 173F and passes over sheave 139 and descends down as rope part 1736 to connect to the equalizer 165 at 175.

It will be understood from the foregoing that the second rope 174 will be reeved in a similar manner over the upper sheaves 132 and the two nest sheaves that are not shown as mentioned above. In the load block the rope 174 will be reeved over sheaves 153, 154 and in rope parts l74a-174f as indicated in FIG. 10. Rope part 174g comes down from the sheave nest to connect with equalizer at l76.

It will be seen that in normal operation of the embodiment shown and described in connection with FIGS. 9 and 10 there are 14 active rope parts supporting the load block 135 and any load that may be on the hook 137. From FIG. 10 it will be seen that the moment of each rope part with respect to the center line C of the load block 135 is such that the combined moment arms of both ropes with respect to each quadrant are equal, not taking into account the two rope parts 1730 and 174g that come down from the sheave nest and connect with the equalizer 165 at 175 and 176, respectively. The moment arms of the two rope parts 1736 and 174g (FIG. 9) will be equal also. Accordingly, in

normal operation the combined moment arms with respect to the center line C of the load block 135 will be essentially balanced in all four quadrants therearound and the load and load block 135 will be subject to little if any twisting or swinging movement.

In the event that one of the ropes 173 or 174 breaks it will be apparent that all of the load will be transferred to the remaining rope including the seven parts thereof. When such transfer occurs the load will settle somewhat due to tilting of the equalizer beam 165 and the load will also swing somewhat so as to be more underneath the half of the drum 136 which has the undamaged rope wound thereon. The vertical settling movement will occur without impact because of the damping effect of the springs 170-170. The swinging movement will be of small magnitude since the rope 173A or 174a, as the case may be, coming down from the drum 136 will be only one active part out of seven.

It will be understood that the embodiment of the invention shown and described in connection with FIGS. 9 and 10 may also have the additional redundancy or double safe features provided in connection with the embodiment shown and described in connection with FIGS. 2-8. That is, sheave guards may be provided underneath the various sheaves in the sheave nest and above the various sheaves in the load block 135; a double drive train may be provided so that the drum 136 is driven from opposite ends; and, safety lugs may be provided at opposite ends of the drum so as to catch the adjacent drum hub in the event of shaft failure.

Additional redundancy or safety features can be provided for in the embodiments shown and described in connection with FIGS. 2-10 and these will be described in connection with FIGS. 12 and 13 wherein a modified equalizer beam and shock absorber arrangement is shown for use in connection with the sheaves in the sheave nest mounted on a crane trolley such as in the embodiment of FIGS. 2-8. Referring to FIGS. 11-12 and equalizer bar or beam is shown which is pivoted at its center on a pivot pin 181 which is supported at one end in an aperture 182 in the trolley load girt 183 and at the other end in an opening in a vertical plate 184 which is parallel to the girt 183. The plate 184 is supported at the top from a cantilever member 185 welded to the girt 183, by means of bolts 186 which extend down through a horizontal flange 187 pair of members 192-192 (FIG. 12) which at their centers have welded therebetween a square block member 193, and to the rear of and in between one plate 192 and the load girt 183, a square spacer block 194. The blocks 193 and 194, together with the members 192-192 all have aligned central openings for receiving a sleeve bushing 195 which fits over the pin 181. I

The plates 192-192 are secured in spaced relation at their opposite ends by plates 196-196 and bottom bumper plates 197-197. The plates 196 are apertured so as to receive the threaded portions of anchor bolts 198-198 formingpart of the assemblies for securement of the opposite ends of ropes 200 and 201 which extend down to sheaves in the load block of the crane. Thus, rope 200 corresponds to rope 121k and rope 201 corresponds to rope 1201-! in the embodiment shown in FIG. 3. The ends of the ropes 200 and 201 are secured in fittings 202-202 of known commercial type which are screwed onto the inner ends of the anchor bolts 198.

It will be seen that by tightening or loosening the nuts 203-203 on the outer ends of the bolts 198 the ropes 200 and 201 may be adjusted as desired so as to maintain the equalizer arm 180 approximately horizontal. The equalizer arm 180 carries a pair of guide sheaves or pulleys 204-204 over which the ropes 200 and 201 run.

Mounted underneath opposite ends of the equalizer arm 180 so as to be engaged by the plates 197 on opposite ends thereof are bumpers 205-205 which are suitably mounted on the load girt 183. Outwardly of each of the bumper assemblies 205 is disposed a microswitch assembly 206 of known commercial type the button 207 of which is placed slightly above the cushion 208 of the adjacent bumper assembly. Each cushion 208 is provided on two sides with plates 210 so as to limit positively the extent to which each cushion 208 can be depressed thereby preventing damage to the microswitches 206 the buttons 207 of which can be de-' pressed below the tops of the plates 210.

The purpose of the microswitches 206 is to provide an electrical signal in the event either bumper 205 is engaged by the bumper plate 197 on the adjacent end of the equalizer arm 180. The signal may be used, for example, to turn off the crane motors, sound an alarm, illuminate a warning light, etc. This can happen either when one of the ropes 200 or 201 breaks and the equalizer arm 180 tilts or it can happen if the ropes stretch unequally and so that the equalizer bar is no longer horizontal but is tilted too much one way or the other.

A pair of hydraulic cylinder units 212-212 are pivotally supported underneath the equalizer arm 180 on opposite sides of the pivot pin 181 by means of pins 213-213 which are carried on brackets 214-214 supported on the load girt 183. The upper ends of the piston rods 215 of the cylinders 212 are connected by pins 216-216 extending through apertures in the equalizer arm plates 192-192 and through the fittings 217-217 mounted on the upper ends of the piston rods 215.

Each of the cylinders 212 has a port at its-upper end which is provided with a needle valve having an adjusting screw 218. Each port is connected by means of a conduit indicated in broken line 220 to a pressurized accumulator 221 of known commercial type which serves to maintain any desired pressure on the fluid in the-system. With this arrangement it will be seen that if the forces applied to the equalizer arm by the ropes 200 and 201 become unbalanced for any reason, such as one of the ropes breaking or stretching unduly, the piston in one of the cylinders 212 will rise while the piston in the other unit will fall, depending upon which way the equalizer arm or beam 180 tilts. In either case this movement is resisted or damped to the desired degree depending upon the setting of the needle valves 218. In other words, the hydraulic fluid has to be forced through restricted orifices and thereby sudden movement of the equalizer arm in either direction is prevented.

It will be seen that in the event the equalizer arm 180 should break or fail for any reason, it will be caught and supported at the center by means of the box-like frame structure provided by the load girt 183 and members and elements 184, 185 and 191-191, while it will-be supported at the opposite ends by the bumper assemblies 205-205.

In FIGS. 13 and 14 two modified forms of equalizer beam or arm assemblies are shown which can be used in place of the equalizer arm assemblies shown and described in connection with FIGS. 2-12. In FIG. 13 there are two relatively short equalizer arms 222 and 223 each of which is pivotally mounted on a pin 224 and 225, respectively, adjacent its outer end. The inner end of each equalizer arm carries a guide pulley 226 and 227, respectively, over which extend crane drum ropes 228 and 229, respectively. The ends of the crane ropes are secured in known manner to adjustable anchor bolt assemblies 230-231, respectively, carried by the equalizer arms. Hydraulic cylinder units 232 and 233 are pivotally mounted on pins 234 and 235, respectively, underneath each of the arms 222 and 223. The piston or connecting rod of each cylinder unit is pivotally connected at 236 and 237 respectively carried by the arms 222 and 223. The bottom ends of cylinder units 232 and 233 have ports which are interconnected by means of a line 238 provided with an adjustable restrictive orifice indicated diagrammatically at 240. The upper ends of each of the cylinder units 232 and 233 will be connected to a suitable reservoir with the connections being indicated at 241 and 242, respectively. Underneath each of the equalizer arms 222 and 223 a bumper 243 and 244, respectively, is mounted so as to limit the downward tilting movement of the arms after such movement has been allowed to occur only slowly by the throttling action of the orifice as the fluid is discharged from one of the cylinders 232 or 233 and transmitted to the other depending upon which of the equalizer arms is tilted downwardly and which is simultaneously forced upwardly.

Referring to FIG. 14 an equalizer arrangement is shown diagrammatically therein generally at 245 which comprises a horizontal frame member 246 mounted for horizontal shifting movement between sets of supporting rollers 247-247 and 248-248. Adjustable anchoring bolt assemblies 250 and 251 are mounted on opposite ends of the member 246 and are adapted to have secured thereto ends of crane drum ropes 252 and 13 253, respectively. The structure includes guide pulleys 254-255 and initially the bolts 250-251 will be adjusted so that the member 246 is centered with respect to the center of the crane drum (not shown).

The shock absorbing action is provided by a stationary double-acting cylinder unit 256 having a single piston 257 from the opposite sides of which piston rods 258 and 259 project. Each piston rod is in abutting engagement with a depending plate 260 and 261, respectively, so that when the beam or member 246 has occasion to shift in either direction when one of the ropes 252 or 253 breaks or stretches, the piston 257 will be correspondingly shifted in one direction or the other relative to the cylinder 256.

The piston 257 has a throttling orifice 262 so as to provide a dampening or shock absorbing action resisting the free movement of the piston 257 within the cylinder unit 256 and thereby imparting a dampening and shock absorbing action to the shifting of the member 246. Bumpers 263-and 264 are mounted so as to be engaged by the moving frame or beam 246 if the movement exceeds the predetermined amount that is determined as adequate for proper functioning of the equalizer 246.

We claim:

1. In a crane comprising a horizontal drum having two separate ropes wound thereon with one end of each rope secured to said drum to one of the opposite sides of the mid-portion thereof, an upper sheave nest having at least two parallel nest sheaves, a load block suspended beneath said sheave nest having at least one pair of load block sheaves on each side of a vertical center plane including the vertical center line of said block, and an equalizer having the other two ends of said ropes secured thereto to one of the opposite sides of the mid-point thereof, the improvements comprising having said load block sheaves disposed in planes substantially parallel to said vertical center plane with the opposite ends of the horizontal diameter of each of said load block sheaves coinciding with the locii of two corners of a horizontal quadrilateral the locii of the remaining two corners of which coincide with the opposite ends of the horizontal diameter of one of said load block sheaves disposed on the opposite side of said vertical center plane, having each of said two ropes having parts reeved over one of said nest sheaves and under two of said load block sheaves which are disposed on opposite sides of said vertical center plane the horizontal diameters of which form two opposite sides of one of said quadilaterals, having each sheave in said upper sheave nest in a vertical plane at right angles to said vertical center plane, having at least two sheaves in said upper sheave nest horizontally offset with one of said ropes reeved over one offset sheave and the other rope being reeved over the other offset sheave, said equalizer extending in a generally horizontal direction at right angles to said vertical center plane, and having shock absorber means operatively connected with said equalizer so as to dampen the shifting movement thereof which occurs when either of said ropes breaks.

2. The improvement of claim 1 wherein said quadrilaterals are trapezoids.

3. The improvement of claim 2 wherein said trapezoids are substantially congruent.

4. The improvement of claim 1 wherein said equalizer is carried on the crane super-structure.

5. The improvement of claim 1 wherein said equalizer is carried on said crane block.

6. The improvement of claim 1 wherein the diagonally opposed comers of each quadrilateral are approximately equidistant from said vertical center line.

7. The improvement of claim 1 wherein said equalizer is substantially parallel with said drum and said one end of each rope attached to said equalizer has its opposite end secured to said drum on that side of the midportion thereof which is the more removed from where the said one end is attached to said equalizer.

8. The improvement of claim 1 wherein said equalizer comprises a beam pivotally mounted intermediate its ends and wherein a shock absorber is operatively connected to each end of said equalizer beam so as to dampen the movement thereof.

9. The improvement of claim 1 wherein said equalizer comprises a pair of spaced aligned arms each of which is pivotally mounted adjacent its outer end and wherein a shock absorber is operatively connected to each of said arms so as to dampen the movement thereof.

10. The improvement of claim 1 wherein said equalizer comprises an elongated frame member mounted for horizontal reciprocal movement and wherein a shock absorber is operatively connected with said frame member to dampen the movement thereof.

11. In a crame comprising a drum, an upper sheave nest having at least two nest sheaves, an equalizer, and a load block suspended beneath said sheave nest and having at least two load block sheaves on each opposite side, the improvements comprising, having two separate ropes with one rope wound on and secured at one end to one longitudinal portion of the drum and with the other rope wound on and secured at one end to the other longitudinal portion of the drum, the opposite ends of each rope being secured to said equalizer on opposite sides of the pivot or mid-point thereof, and with each rope intermediate its ends being reeved over at least one nest sheave and under at least one load block sheave on each side of said block, and a dual load hook carried by said load block having separate load attaching means and separate substantially co-incident load paths.

12. In the crane called for in claim 11 the further improvement comprising a sheave guard under each nest sheave and over each load block sheave.

13. In the crane called for in claim 11 the further im provement wherein said crane drum is driven from opposite ends through separate gear trains.

14. The crane called for in claim 11 the further improvement wherein said drum has a hub at each opposite end and a safety block is mounted under the hub on each opposite end of said drum.

15. In the crame called for in claim 1 1 the further improvement wherein said crane has a load girt and said equalizer comprises a beam pivotally supported on a pin carried by the load girt of the crane and said equalizer beam is framed in by structural members that will catch and support it in the event said pin fails. 

1. In a crane comprising a horizontal drum having two separate ropes wound thereon with one end of each rope secured to said drum to one of the opposite sides of the mid-portion thereof, an upper sheave nest having at least two parallel nest sheaves, a load block suspended beneath said sheave nest having at least one pair of load block sheaves on each side of a vertical center plane including the vertical center line of said block, and an equalizer having the other two ends of said ropes secured thereto to one of the opposite sides of the mid-point thereof, the improvements comprising having said load block sheaves disposed in planes substantially parallel to said vertical center plane with the opposite ends of the horizontal diameter of each of said load block sheaves coinciding with the locii of two corners of a horizontal quadrilateral the locii of the remaining two corners of which coincide with the opposite ends of the horizontal diameter of one of said load block sheaves disposed on the opposite side of said vertical center plane, having each of said two ropes having parts reeved over one of said nest sheaves and under two of said load block sheaves which are disposed on opposite sides of said vertical center plane the horizontal diameters of which form two opposite sides of one of said quadilaterals, having each sheave in said upper sheave nest in a vertical plane at right angles to said vertical center plane, having at least two sheaves in said upper sheave nest horizontally offset with one of said ropes reeved over one offset sheave and the other rope being reeved over the other offset sheave, said equalizer extending in a generally horizontal direction at right angles to said vertical center plane, and having shock absorber means operatively connected with said equalizer so as to dampen the shifting movement thereof which occurs when either of said ropes breaks.
 2. The improvement of claim 1 wherein said quadrilaterals are trapezoids.
 3. The improvement of claim 2 wherein said trapezoids are substantially congruent.
 4. The improvement of claim 1 wherein said equalizer is carried on the crane super-structure.
 5. The improvement of claim 1 wherein said equalizer is carried on said crane block.
 6. The improvement of claim 1 wherein the diagonally opposed corners of each quadrilateral are approximately equidistant from said vertical center line.
 7. The improvement of claim 1 wherein said equalizer is substantially paraLlel with said drum and said one end of each rope attached to said equalizer has its opposite end secured to said drum on that side of the mid-portion thereof which is the more removed from where the said one end is attached to said equalizer.
 8. The improvement of claim 1 wherein said equalizer comprises a beam pivotally mounted intermediate its ends and wherein a shock absorber is operatively connected to each end of said equalizer beam so as to dampen the movement thereof.
 9. The improvement of claim 1 wherein said equalizer comprises a pair of spaced aligned arms each of which is pivotally mounted adjacent its outer end and wherein a shock absorber is operatively connected to each of said arms so as to dampen the movement thereof.
 10. The improvement of claim 1 wherein said equalizer comprises an elongated frame member mounted for horizontal reciprocal movement and wherein a shock absorber is operatively connected with said frame member to dampen the movement thereof.
 11. In a crame comprising a drum, an upper sheave nest having at least two nest sheaves, an equalizer, and a load block suspended beneath said sheave nest and having at least two load block sheaves on each opposite side, the improvements comprising, having two separate ropes with one rope wound on and secured at one end to one longitudinal portion of the drum and with the other rope wound on and secured at one end to the other longitudinal portion of the drum, the opposite ends of each rope being secured to said equalizer on opposite sides of the pivot or mid-point thereof, and with each rope intermediate its ends being reeved over at least one nest sheave and under at least one load block sheave on each side of said block, and a dual load hook carried by said load block having separate load attaching means and separate substantially co-incident load paths.
 12. In the crane called for in claim 11 the further improvement comprising a sheave guard under each nest sheave and over each load block sheave.
 13. In the crane called for in claim 11 the further improvement wherein said crane drum is driven from opposite ends through separate gear trains.
 14. The crane called for in claim 11 the further improvement wherein said drum has a hub at each opposite end and a safety block is mounted under the hub on each opposite end of said drum.
 15. In the crame called for in claim 11 the further improvement wherein said crane has a load girt and said equalizer comprises a beam pivotally supported on a pin carried by the load girt of the crane and said equalizer beam is framed in by structural members that will catch and support it in the event said pin fails. 